High frequency electrical apparatus



1943- R. H. VARIAN ET AL 2,307,036

HIGH FREQUENCY ELECTRICAL APPARATUS Original Filed May 7, 1941 2 sheets sheet 1 INVENTORS RUSSELL H.VARIAN BY WILLIAM W. HANSEN MZ M THEIR ATTORNEY an. 5, 143. R, H. VARIAN ETAL 2,307,036

HIGH FREQUENCY ELECTRICAL APPARATUS Original Filed May 7, 1941 zsheetksheet 2 IN VEN TORS RUSSELL H. VARIAN WILLIAM W. HANSEN THEIR ATM Patented Jan. 5, 1943 mtmttt HIGH FREQUENCY ELECTRICAL APPARATUS Russell H. Varian, West Hempstead, and William W. Hansen, Garden City, N. Y., assignors to The Board of Trustees of The Leland Stanford Junior University, Stanford University, Calif., a corporation of California Application May 7, 1941, Serial No. 392,248

8 Claims.

The present invention relates, generally, to the control of electron beams by electromagnetic fields for the excitation of electric circuits, and has reference, in particular, to novel electrical high frequency apparatus in which electron beams are subjected to displacement by electromagnetic fields confined in hollow conductors or in conductor arrangements capable of maintaining standing electromagnetic waves.

The present invention described and claimed herein was initially disclosed in application Serial No. 193,268, filed March 1, 1938, now Patent No. 2,272,165, issued February 3, 1942, in the names of Russell H. Varian, William W. Hansen and Lindsay M. Applegate, for High frequency electrical apparatus. The embodiments of the present invention utilize some of the elements of Patent No. 2,190,712, February 20, 1940, William W. Hansen, and co-pending applications Serial No. 168,355, Russell H. Varian, filed October 11,

1937, Patent No. 2,242,275, May 20, 1941, and Serial No. 315,324, Russell H. Varian, William W. Hansen and Lindsay M. Applegate, filed January 24, 1940, Patent No. 2,275,480, May 10, 1942, to which patents the present invention is related.

In Patent No. 2,190,712 there is disclosed a hollow conducting resonant chamber of novel type having characteristics that render the same particularly adaptable to use in providing oscillating circuits having frequencies of the order of 10 cycles or more per second. When operating at frequencies of the order of 10 cycles per second such resonant circuits are of outstanding im portance. In the present invention this type of circuit is used as shown in the drawings because of its convenience and usefulness. The present invention can be embodied without the special resonant circuits of the Patent No. 2,190,712, but not in general without some sacrifice of convenience and efiiciency. The resonator of Patent No. 2,190,712 is essentially a hollow chamber with conducting walls capable, together with coupled apparatus, of sustaining electromagnetic oscillations as a very efiicient resonant circuit. It is distinguished from other types of oscillating circuits by its mode of operation even more than by its appearance. It operates so that an electromagnetic field is produced inside the closed conducting chamber by currents confined to the walls of the chamber surrounding the contained field.

In Patent No. 2,242,275 there is disclosed means for controlling a beam of electrons by causing it to pass through an electric field, particularly'a field with its electric component parallel to the axis of the electron beam to which is parallel also the axis of a hollow resonator containing the field. Such a beam is made to produce radio frequency oscillations. That invention includes among other things the combination of a hollow resonator and a beam of electrons passing through it for control purposes. The present invention uses this combination in some embodiments thereof.

This invention has for its principal object the provision of a novel high frequency electrical apparatus adapted for the excitation of electric circuits by periodically transversely, radially, or rotationally displacing an electron beam, the displacement of which requires less power than that rendered available as high frequency energy as the result of the deflection of the beam, whereby the energy of an electron beam is converted into an alternating current of any desired high frequency.

Another object of the present invention is to provide novel apparatus for the control of electron beams by causing transverse types of displacement, resulting in the excitation of circuits by beams periodically transversely displaced, and the amplification of power by the use of, transversely displaced electron beams in suitable circuits.

Still another object of the present invention is the provision of a novel high frequency electrical apparatus with associated circuits for performing all the principal functional operations ordinarily associated with the generation, amplification, modulation, transmission, reception and detection of high frequency oscillations.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings,

Fig. 1 is an embodiment of our invention and a showing of one of its applications in which an electron beam is laterally displaced in an electric field so that the energy of which beam is absorbed in maintaining an electromagnetic field in a hollow resonator, which field is used for accelerating electrons.

Fig. 2 is a simplification of the structure of Fig. 1.

Similar characters of reference are used in all of the above figures to indicate corresponding par s.

In its essential embodiment our invention employs an electron beam that is given periodic transverse displacement for control as is shown in Figs. 1 and 2. In Fig. 1 a beam of electronsds accelerated from an-emitter 2! by a grid 22 and is projected between a pair of deflecting plates 24 and 25 into a resonator 26 where the electrons impinge alternately on two plates 21 and 28 after entering through grid 30". The electron beam is shifted from one plate to the other by an alternating field caused to exist between plates 24 and 25 which receive excitation from a loop 29 inside resonator 26 and a symmetrically arranged pair of leads 3i and 32 outside the resonator. These leads would ordinarily be close together or in the form of a concentric line but are shown far apart for convenience in the drawings. The energy of the electron beam is coupled into the resonator 26 by a pair of coupling loops 33 and 34 connected to the plates 21 and 28.

In the process of oscillation taking place in the structures of Figs. 1 and 2 the electron beam energy is absorbed alternately in the fields between grid 30" and the plates 21 and 28, conveying pulses of energy alternately to the coupling loops 33 and 34. The arrangement provides a pulsation of current in the loops 33 and 34 every half cycle, the alternate pulsations producing magnetic fields of opposite polarity.

Resonator 26 is illustrated as a right circular cylinder whose axis is horizontal and transverse of the figure. The faces 30 and 30 in such case are circular and they are at a uniform distance apart as the heads of a drum. The openings where the electron beam 23 enters are in the curved side of the drum-shaped container. In it, the electric field exists most strongly in the center extending from side to side in the figure. across the space between the two sides 36 and 30'. The magnetic field in the resonator at a section corresponding to that of the plane of the drawing exists perpendicularly to the plane of the drawing and is strongest in the region of the curved sides of the resonator, where it is ln-' terlinked with the coupling loops. The elements 2| to 34. inclusive, cause, as a result of powerful oscillations in the resonator 26, high instantaneous difierences of potential to exist between the side 36 and side 30' of the resonator 26. This difference of potential is used to accelerate electrons to high velocity for various applications one of which is illustrated.

An electron emitter 4| and an accelerating grid 42 project a stream of electrons 43 between two deflecting plates 44 and 45 into the resonator 26 through an opening 35 in the side 30. If the resonator is oscillating, the plates 44 and 45 excited thereby will swing the beam of electrons 43 back and forth so that during alternate half cycles the electrons will alternately miss and enter the hole 35 in the side 30 of the resonator. The polarity of the plates 44 and 45 is arranged so that the electrons enter and pass through the resonator during the half cycles when the integrated value of the accelerating force on an electron is a maximum. This occurs generally when the electrons are admitted to the hole 35 of resonator 26 just as the other side 30' thereof begins to accumulate a positive charge. The potential diiference between the grid 42 and the emitter 4| is made great enough so that the electrons enter the resonator with a fairly high velocity and preferably of the order of ninetenths .of the velocity of light.

The dimension of the resonator 26 from the side 36 to the side 36 is made a little less than the distance a particle with the speed of light will travel in a half period of the resonator oscillation. Thus, any electron whose velocity approaches that of'light can make several circuits from side to side of the resonator 26 and back without getting out of phase with the oscillations of the system inasmuch as the maximum velocity any electron can attain will be less than that of light. An electron admitted to the resonator through the hole 35 crosses the resonator and reaches the side 36' in about a half period. It passes through the hole 36 and enters the field of a magnet 46 where its motion is reversed. The electron, after the direction of its motion has been reversed by the field of magnet 46, reenters the resonator 26 through a hole 36'. The electron then travels back to the side 30 and through a hole 35' in the next half period and is reflected again by a second magnet 41. This is repeated as many times as required to get the electron velocity desired. In Fig. 1 there are three reflections at the side 30' and two at the side 30 of the member 26. After the last reflection at the side 30 the electron passes through an aperture 35" in side 36 and, passing below magnet 41, impinges upon a target 48 where the impact is shown for producing X-rays.

Fig. 2 shows an arrangement for producing X-rays using only a single trip of the beam through the resonator 26 for the acceleration of electrons. The structure of Fig. 2 is similar to that of Fig. 1 except for the different mechanical arrangement resulting from the omission of the magnets 46 and 41.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In combination, means for producing an electron beam, means for producing high frequency transverse oscillations of the beam, means for confining standing electromagnetic waves, mutually spaced means within said confining means for consecutively collecting the electrons of the beam in accordance with its instantaneous transverse position, and conducting means connected to said mutually spaced means for leading the currents produced by the collected beam through a portion of said confined standing electromagnetic waves in such a way that said currents individually link magnetic fiux lines in such sense as to enhance the strength of said system of standing electromagnetic waves.

2. Means for producing electrons of uniformly high velocity comprising means for producin a system of confined standing electromagnetic waves, means for projecting a beam of electrons therethrough, means for producing alternating lateral displacement of said electron beam at the frequency of said system of confined standing electromagnetic waves, and means excluding said beam of electrons from said system of confined standing electromagnetic waves except when said lateral displacement of said beam of electrons has certain desired values.

3. In combination, means for producing an electron beam, means for producing high frequency lateral displacement of said beam, cavity resonator means including means for effecting entry of said beam into said resonator, means for driving the latter. and means for exciting said beam displacement means from said cavity resonator means.

4. Apparatus of the character described for producing high velocity electrons comprising, a hollow resonator, means for exciting said resohator to set up an ultra high frequency alternating electromagnetic field therein, means for producing a beam of electrons, means for setting up an alternating electric field transversely of said electron beam for swinging said beam transversely, said hollow resonator being apertured for receiving said beam during a portion ,of it swinging movement, said alternating field being so phased with respect to the standing field within said resonator that electrons of said beam enter said resonator in such phase as to be accelerated by the electric component of the resonant field therein, whereby the electrons entering said resonator are speeded up.

5. A high frequency apparatus comprising, a

hollow resonator, means for exciting said resonator, said means including means for producing an electron beam, means excited from said resonator for setting up an alternating electric field for swinging said beam transversely, said resonator being apertured for receiving said swinging beam, and having means therein for absorbing energy from said beam to thereby set up a standv .7. Means for producing high intensity X-rays comprising, a hollow resonator, means for exciting said resonator, means for producing an electron beam, means excited from said resonator for setting up an alternating electric field for swinging said beam transversely, said resonator being apertured for receiving said beam during a portion of its swinging movement, said alternating field being so phased as to cause the portion for producing a pair of electron beams, means excited by said resonator for eifecting transverse swinging movements of said electron beams, one of said beams entering said resonator for setting up and maintaining a standing electromagnetic field therein, the other of said beams entering said resonator during a portion only of its swinging movement, a portion of such latter beam entering said resonator in such phase as to be accelerated by the field therewithin, and means for utilizing said accelerated beam portion after the same again leaves said resonator.

RUSSELL H. VARIAN. WILLIAM W. HANSEN. 

